Environmental and Sustainability Consultants

Hidden Mold Contamination in Homes

hidden mold contamination in homes

Hidden Mold Contamination in Homes

by Leon Levine, CIH

Leaks and moisture problems are a common occurrence in homes, even in new construction.   Pipes could be leaking inside wall cavities without your knowledge. Persistent leaks and moisture issues can lead to hidden mold contamination in homes. Some moisture problems have been associated with modifications in building construction practices since the 1970s. To increase energy efficiency, buildings have become more tightly sealed, potentially resulting in poor ventilation. Without adequate ventilation, moisture may build up indoors creating conditions conducive to mold growth. Musty odors may provide a clue that you have hidden mold. You may also suspect a hidden mold problem if a history of water problems have existed and individuals are complaining of health symptoms.   An experienced environmental health professional such as a certified industrial hygienist (CIH) can conduct a mold investigation to assess the potential indoor environmental quality (IEQ) problem and help resolve the issue.

Sources of Moisture

It is important address leaks immediately and to dry any wet items within 24-48 hours to prevent mold growth. We have found in certain cases where the homeowners went on vacation or did not attend to the house for an extended period of time during which a leak or flood occurred.   Moisture alarms/detectors are highly useful and will alert you of moisture intrusion and/or floods. Once you identify a leak equipment commonly used to dry out building materials includes wet vacs, blowers, dehumidifiers, etc. Moisture problems can occur from any of the following:

– Roof leaks.

– Leaking or condensing water pipes, especially pipes inside wall cavities or pipe chases.

– Leaking fire-protection sprinkler systems.

– Landscaping, gutters and down spouts directing moisture into or under a building.

– High humidity (60% relative humidity); humid air condensing on cool surfaces (sheetrock, etc)

– Unvented combustion appliances such as clothes dryers vented into a garage. (Clothes dryers and other combustion appliances should be vented to the outside.)

– Bathroom exhausts being vented into an unconditioned attic (humid air condensing on rafters, etc.)

hidden mold contamination in homes

Hidden Mold Growth


Some moisture problems are not easy to see. Wall cavities where pipes and wires run (pipe chases and utility tunnels) are common sites of mold growth. Mold is frequently found on walls in cold corners behind furniture where condensation forms. Other possible locations of hidden moisture, resulting in hidden mold growth are:

  • Poorly draining condensate drain pains inside air handling units.
  • Porous thermal or acoustic liners inside duct work.
  • Roof materials above ceiling tiles.
  • The back side of drywall (also known as gypsum board, wallboard, or drywall), paneling, and wallpaper.
  • The underside of carpets and pads.



Vapor Barriers


Many buildings incorporate vapor barriers in the design of their walls and floors. A vapor barrier is a layer of material that slows or prevents the absorption or release of moisture from or into a wall or floor. Vapor barriers must be located and installed properly or the building may have moisture problems.  Vapor barriers can prevent damp or wet building materials from drying quickly enough to prevent mold growth.



Heating Ventilation and Air Conditioning (HVAC) Systems


The building’s air-handling system should be inspected to determine whether it is moldy. Moisture may collect in the ventilation system due to poor condensate pan drainage, poor roof drainage, or high humidity in the ventilation ducts. In some cases, water may enter the ventilation ducts from a leaky pipe. A contaminated ventilation system may spread mold spores throughout the building and should be considered a high priority for investigation and repair. Ventilation system mold contamination should be mitigated as soon as possible in a manner that does not expose building occupants to dust and mold spores.

hidden mold contamination in homes

Mold Inspection

To find hidden mold contamination, a variety of tools are utilized.   One important tool is your nose. If you detect a musty odor in a specific area, there’s a good chance there’s hidden mold. A moisture meter is utilized to check whether surfaces are wet.   The moisture meter will provide a numerical reading indicating a dry, medium wet or extremely wet surface. The moisture meter can also trace the path or extent of a leak based on the measurements. A boroscope is used by probing hidden areas such as wall cavities, crawl spaces, and duct work to inspect for mold contamination. A boroscope contains a video camera at one end of a wire. The CIH can inspect a hidden area by viewing the image displayed on the screen.   Air monitoring can also reveal hidden contamination.   To evaluate airborne spore concentrations spore trap cassettes are utilized. The samples are submitted to an accredited microbiology laboratory. A particle meter can be used to collect a quick screening sample on site.

hidden mold contamination in homes

Health Effects of Mold


The Institute of Medicine (National Academy of Sciences) 2004 report Damp Indoor Spaces and Health is believed to be the most authoritative epidemiological study and evaluation of peer reviewed scientific literature concerning associations between exposure to mold and other allergen/irritants related to damp/wet conditions in indoor environments and adverse health effects. This report concluded that there is sufficient evidence of an association between exposure to mold and other allergens/irritants in damp/wet indoor spaces and the occurrence of upper respiratory tract symptoms, coughing, wheezing, asthma symptoms (in sensitized individuals with asthma), hypersensitivity pneumonitis (in susceptible persons), respiratory infections and fungus-related illnesses (in immunocompromised persons), and colonization and potential lung infection in individuals with chronic pulmonary disorders. Additionally, the World Health Organization determined in their 2009 report entitled Dampness and Mould that “There is sufficient epidemiological evidence of associations between dampness or mold and asthma development, asthma exacerbation, current asthma, respiratory infections (except otitis media), upper respiratory tract symptoms, cough, wheeze and dyspnoea”. Susceptible individuals including infants, children and the immune-compromised are more at risk of health systems from mold exposure.





Water leaks are common and can cause hidden mold contamination in homes.  If these leaks are not addressed immediately it may result in mold contamination and potential health effects.   Active mold growth leads to contaminants being released into the indoor air including spores, beta glucans, and microbial volatile organic compounds (VOCs). Upon exposure, susceptible individuals including infants, children and the immune-compromised are most at risk of experiencing health systems.   It is important fix leaks immediately and to dry items quickly to prevent mold growth; in most cases, items dried within 24-48 hours will not become moldy.   An experienced environmental health professional such as a certified industrial hygienist (CIH) can conduct a mold investigation to assess the potential indoor environmental quality (IEQ) problem and work closely with the owner to eliminate any hazards.


For questions or concerns regarding mold contamination or other indoor environmental quality issues please contact ECOthink Group at info@ecothinkgroup.com or 646 705 1593.

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